Temperature gauge not working

Hi DeputyChief,

This sounds like a wiring issue or an issue with the PCM. However, I suspect wiring because the PCM will run the fans after the engine is shut off just to try and cool the engine quickly. Also, the fact that the fans keep running shows the PCM knows what the coolant temp is. So this means there is an issue with just the gauge to the PCM.

I attached the explanation of the system and it says that it will default to 140 degrees (lowest temperature) if it detects an issue in the coolant temp sensor circuit or the "class 2" communication with the PCM. Class 2 communication is just a format of wiring called a Bus network.

We need to pull any codes in the system and if there are none, we need to test the wires from the temperature sensor to the PCM for a short or open circuit. Then from the PCM to the IPC if there was no issue there.

Let's start with getting codes and then we can get into how to test the wires. If you have access to a scan tool that can monitor the bus network, that will be the easiest way to figure this out but if not, we can use a voltmeter.

Let me know if there are codes and we can go from there. Thanks